Optical circuit switches (OCSs) are the heart of optical circuit switching networks. An OCS includes a number of optical collimators which direct optical signals into and out of optical fibers coupled to the OCS. The OCS further includes a mirror array which can be a micro-electro-mechanical system (MEMS) based micro-mirror array that can selectively direct optical beams from individual optical fibers coupled to input collimators to selected optical fibers coupled to output collimators. The MEMS mirror angles required for optimal fiber coupling efficiency between input and output optical fibers can be monitored and corrected using a control system, including a camera system that monitors light reflecting off the mirrors of the MEMS mirror array.